Nav: Home

Preserved leaves reveal 7000 years of rainfall and drought

February 15, 2019

A study by University of Adelaide researchers and Queensland Government scientists has revealed what south-east Queensland's rainfall was like over the last 7000 years - including several severe droughts worse and longer lasting than the 12-year Millennium Drought.

The study - published in Scientific Reports - used preserved paper-bark tea tree leaves from North Stradbroke Island's Swallow Lagoon that have been collecting in the sediment for the past 7700 years.

The leaves - analysed for chemical variation - provided a wealth of information on the El Niño-Southern Oscillation (ENSO) and how it was impacted by major climate changes over the millennia, including the Little Ice Age from about 1450 to 1850.

Researchers found a generally wet period about 5000 to 6000 years ago - indicating a more consistent La Niña-like climate.

"This changed to a more variable and increasingly drier climate about 3000 years ago - highlighting a strengthened El Niño phase,'' says Associate Professor John Tibby from the University of Adelaide's Geography Department.

"There were substantial droughts during this phase, drier than the Millennium Drought which south-east Australia experienced from 1997-2009. In fact, from what we can ascertain, the probability of a drought worse than the Millennium Drought is much higher than the current prediction of one in 10,000 years.

"Our rainfall reconstruction suggests that it may be as much as 10 times more likely."

Associate Professor Tibby said the Little Ice Age, which ended about the time south-east Queensland was settled, was unusually wet.

The study was possible because Swallow Lagoon contains a continuous sequence of leaves from a single species of tree. Variations in the chemistry of these leaves allowed scientists to reconstruct past rainfall.

"Finding leaves preserved in lake sediments of this age is rare, and they can tell us a lot about the environment. For instance, the carbon isotope composition - or chemistry - of the leaves can tell us about the degree of moisture stress experienced by the plants when the leaves were growing,'' says Dr Cameron Barr from the University of Adelaide.

"So, in effect, we can use leaf carbon isotope composition to infer rainfall through time. Since North Stradbroke Island is in a part of Australia that is very sensitive to ENSO, our study is able to document ENSO history."
-end-


University of Adelaide

Related Ice Age Articles:

Paintings, sunspots and frost fairs: Rethinking the Little Ice Age
The whole concept of the 'Little Ice Age' is 'misleading,' as the changes were small-scale, seasonal and insignificant compared with present-day global warming, a group of solar and climate scientists argue.
Ice age thermostat prevented extreme climate cooling
During the ice ages, an unidentified regulatory mechanism prevented atmospheric CO2 concentrations from falling below a level that could have led to runaway cooling, reports a study conducted by researchers of the ICTA-Universitat Autònoma de Barcelona and published online in Nature Geoscience this week.
Simple rule predicts when an ice age ends
A simple rule can accurately predict when Earth's climate warms out of an ice age, according to new research led by UCL.
How an Ice Age paradox could inform sea level rise predictions
New findings from the University of Michigan explain an Ice Age paradox and add to the mounting evidence that climate change could bring higher seas than most models predict.
Inception of the last ice age
A new model reconstruction shows in exceptional detail the evolution of the Eurasian ice sheet during the last ice age.
Ice age vertebrates had mixed responses to climate change
New research examines how vertebrate species in the eastern United States ranging from snakes to mammals to birds responded to climate change over the last 500,000 years.
Why does our planet experience an ice age every 100,000 years?
Experts from Cardiff University have offered up an explanation as to why our planet began to move in and out of ice ages every 100,000 years.
Siberian larch forests are still linked to the ice age
The Siberian permafrost regions include those areas of the Earth, which heat up very quickly in the course of climate change.
Mars is emerging from an ice age
Radar measurements of Mars' polar ice caps reveal that the mostly dry, dusty planet is emerging from an ice age, following multiple rounds of climate change.
New ice age knowledge
An international team of researchers headed by scientists from the Alfred Wegener Institute has gained new insights into the carbon dioxide exchange between ocean and atmosphere, thus making a significant contribution to solving one of the great scientific mysteries of the ice ages.

Related Ice Age Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Changing The World
What does it take to change the world for the better? This hour, TED speakers explore ideas on activism—what motivates it, why it matters, and how each of us can make a difference. Guests include civil rights activist Ruby Sales, labor leader and civil rights activist Dolores Huerta, author Jeremy Heimans, "craftivist" Sarah Corbett, and designer and futurist Angela Oguntala.
Now Playing: Science for the People

#520 A Closer Look at Objectivism
This week we broach the topic of Objectivism. We'll be speaking with Keith Lockitch, senior fellow at the Ayn Rand Institute, about the philosophy of Objectivism as it's taught through Ayn Rand's writings. Then we'll speak with Denise Cummins, cognitive scientist, author and fellow at the Association for Psychological Science, about the impact of Objectivist ideology on society. Related links: This is what happens when you take Ayn Rand seriously Another Critic Who Doesn’t Care What Rand Thought or Why She Thought It, Only That She’s Wrong Quote is from "A Companion to Ayn Rand"